Table of Contents
Any business user-friendly application logic can be divided as:
Tiers demonstrates this logic division on the web-based business application example. A high-level view of the Tiers architecture:
- Web layer
Is responsible for GUI showing, user input control, converting GUI events to calls to the business components.
- Business layer
Is responsible for business rules support, concurrent access management, persistent model constraints check.
- Persistent layer
Is responsible for persistent object model support: load from / save to data storage.
Every layer will be described in the details below.
Web layer main components:
Component responsibilities:
HTML page: user view of system data/images/controls/navigation, JavaScript/CSS inclusion.
JavaScript: simple user input control that do not require server-side execution.
CSS: HTML page layout properties.
Maverick framework:
does Web layer initialization: maverick.xml parsing, XSL stylesheets precompiling/caching, Controller singletons creation.
populates Form objects from HttpRequest.
dispatches request processing to corresponding Controller.
converts created Model to DOM form, applies XSL to DOM, returns result response to Browser.
maverick.xml: URL to (Controller,XSL stylesheets) mapping configuration, Maverick framework customization parameters.
XSL stylesheet: Model DOM form to HTML page transformation rules.
Form: HttpSession-stored JavaBean object populated from HttpRequest, contains GUI web form state.
Controller: Form creation, converting GUI events to calls to the business components, Model building, XSL stylesheet selection.
Model: JavaBean object presentation of GUI data, includes Form.
Used interfaces/protocols:
HTTP(S): Servlet container <-> Browser
DOM,JAXP: Java <-> XSL stylesheet
RMI: Controller <-> Business component
JNDI: Business component lookup
Business layer main components:
Component responsibilities:
Business logic bean: business methods implementation, concurrent access control, persistent model constraints check.
Data access object (DAO): Java API to persistent model, object queries construction.
Tester: functional testing of Business logic bean via remote interfaces.
Used interfaces/protocols:
Hibernate Query Language, Hibernate Session API: DAO <-> Persistent layer
RMI: Tester <-> Business logic bean
JNDI: Business logic bean lookup, Hibernate service lookup
Persistent layer main components:
Component responsibilities:
Initializer: initial persistent data creation via Persistent objects, Hibernate Session API.
Hibernate service: object/relational persistence and query service, persistent objects storing to /loading from relational database.
Connection pool service: database connections cache.
Relational database server: persistent data storage, simple entities relationship constraints support.
Used interfaces/protocols:
Hibernate Query Language, Hibernate Session API: Initializer <-> database
SQL queries over TCP/IP: Hibernate <-> database
JNDI: connection pool service lookup